I wanted to put the soiled litter in my Gorilla cart, but was concerned it would be too heavy.
I don't know what size Gorilla cart you have, but the 7 cubic foot one sold here has a capacity of 1,200 pounds. No way you could load that much soiled litter in a Gorilla cart. The litter is just not that heavy.
I didn't want to damage my door sill so I moved the litter from the wheelbarrow using a small garden cart.
To protect the door sill, you could build a short ramp up and over the sill and back down the other side. Just some scrap lumber would do the job. Of course, that depends on your door sill setup.
Here's a picture of that type of ramp designed for a wheelchair, which also protects the original door sill...
I had to build a pallet wood ramp to get up and into my chicken run. I have about 12 inches of compost litter at my main gate, and I needed a ramp to get my cart into the chicken run. I'm just not back strong enough anymore to muscle a loaded cart up that high...
I filled it about 2/3 so I could lift it over the sill and dump it in the bigger cart.
Have you considered something like muck buckets?
That's what I use when I clean out my chicken coop. Then I carry them to my chicken run and dump them.

Another option to consider might be to use the standard 5-gallon buckets...
I fill my 5-gallon buckets with 25 pounds of chicken feed and have never broken a handle or the plastic on them. They are much stronger than the cheap WalMart muck buckets I bought. There is no way soiled litter would be heavy enough to break my 5-gallon buckets. They only problem is that they cannot hold as much volume as a muck bucket in one load. So you would have more trips to get the same work done. That may or may not be a good thing for you.


That sale is over, but they will probably have another bucket weekend special in 2-3 months. I like free buckets.
I have to add here that I found a use for a shovel I'd bought at Habitat for Humanity thrift store a couple years ago. It was perfect for getting the dregs of soiled litter out of the wheelbarrow. And it was only $2!

That's looks like a perfect shovel for a small, tight, job. Great find for only $2.00!
